2016/02/23 by Kamal Selvam, Jorge Peixinho, Ashley P. Willis +1
Chemical Engineering · Computer Science · Engineering · Physics and Astronomy · #Axial symmetry #Azimuth #Fluid Dynamics and Turbulent Flows #K-epsilon turbulence model #Nonlinear Dynamics and Pattern Formation #Perturbation (astronomy) #Reynolds number #Rheology and Fluid Dynamics Studies #Tourbillon #Turbulence #Vortex #physics.flu-dyn
paper · pdf · doi:10.1088/0169-5983/48/6/061418
published as Fluid Dynamics Research, 48, 061418 (2016) · 12 pages, 7 figures, presented in BIFD, Paris 2015
arxiv created 2016/02/23 · openalex created_date 2016/06/24 · openalex publication_date 2016/11/07 · arxiv updated 2019/01/08 · openalex updated_date 2026/08/05
We report the results of three-dimensional direct numerical simulations for incompressible viscous fluid in a circular pipe flow with a sudden expansion. At the inlet, a parabolic velocity profile is applied together with a finite amplitude perturbation in the form of a vortex with its axis parallel to the axis of the pipe. At sufficiently high Reynolds numbers the recirculation region breaks into a turbulent patch that changes position axially, depending on the strength of the perturbation. This vortex perturbation is believed to produce a less abrupt transition than in previous studies, which applied a tilt perturbation, as the localised turbulence is observed via the formation of a wavy structure at a low order azimuthal mode, which resembles an optimally amplified perturbation. For large vortex amplitude, the localised turbulence remains at a constant axial position. It is further investigated using proper orthogonal decomposition, which indicates that the centre region close to the expansion is highly energetic.